Tenses confusion

Native speakers, be so kind to check whether I used Past Simple or Present Perfect correctly! I've done a really huge exercise but still have some uncertainty on a number of sentences. So here they are: 

1. Simon is not at home. He’s gone to a football match.
2. I’ve ordered a taxi. So we’ll be on time.
3. Peter hasn’t eaten all the bread and butter. He’s left some on the plate.
4. My watch has stopped. I must take it to the watchmaker’s.
5. We’ve run out of sugar. Can you go and get some?
6. Why are you limping? – I’ve twisted my ankle.
7. I’ve lost a button. I don’t suppose I’ll ever find it.
8. All the shirts you sent your father have fit him perfectly so far.
9. John, whose grades are the highest in the school, received a scholarship. 
10. Jerry has failed his exams. He’ll have to take them again.
11. My computer has broken down again. It’s time for me to buy a new one.
*12. I can’t afford a holiday abroad until I've paid back all my debts. 

* I don't understand completely what they wanted me to do in the last sentence as for me the form should be just "pay" i.e. Present Simple --> I can’t afford a holiday abroad until I pay back all my debts.

Honestly, as an American, I can say that we would generally use Present Simple in this case as well.